1. Field of the Invention
This invention relates to apparatus for providing pulsed energization of gaseous discharge tubes and in particular, to the use of such radiation produced thereby in the in situ curing (e.g., polymerization) of small quantities of synthetic resins such as may be used as dental restoratives.
2. Description of the Prior Art
The use of UV radiation for curing synthetic resins is well recognized, and has been heretofore exploited in a variety of applications. Due to the limitations of the intensity and energy densities of typical UV sources, including the sun, such applications have primarily been directed to systems where relatively long cure times are practical, i.e., typically on the order of hours or significant fractions thereof.
Nonetheless, where the amounts of resin to be cured are sufficiently small, attempts have been made in the past to direct UV radiation onto such amounts to effect in situ cure even where very rapid curing is required, such as where it is virtually impossible to maintain the physical placement and environment proximate the resin constant for more than a few seconds.
One such application area lies in the field of dental restoratives, in which a synthetic resin composition having a putty-like consistency is inserted into cavities of teeth and is cured in situ to form strong fillings and coatings. In another application, a much more fluid composition, for example, in the range of several hundred centipoises, may be applied as a surface coating to occlusive surfaces to fill in pits and fissures, whereupon the coating is cured in a similar fashion. A major problem in effecting such in situ UV curing of dental resins lies in the difficulty in directing an appropriate quantity of radiation suitable for such curing into the location of the resin in a fashion which is acceptable from technological, convenience, and patient safety viewpoints.
For example, as depicted in French Pat. No. 2,305,092, issued On Mar. 19, 1976, to Donald Allan Gonser, one proposed device for such an application includes a super-atmospheric non-confined Xenon arc lamp which is enclosed in housing adapted to be hand held, and to which is fitted a quartz rod for conducting UV light from the source into an oral cavity. The device further includes electrical circuitry which is desirably located in a remote enclosure for generating electrical pulses which are coupled to the lamp via a coaxial cable. Such a device is said to optimize the production of desirable radiation, i.e., that within the 320-390 nm range, while minimizing the amount of heat produced. However, it has been found that a configuration such as there described is limited in the luminous intensity which can be directed onto a dental filling, as well as in the lack of control over the uniformity in intensity between successive flashes, depending upon operating voltages and history of the flash lamp.
Another device intended for similar applications is depicted in German Pat. No. 2,711,962 (Buzzi et al). In that publication, rechargeable Xe flash tubes, together with quartz rods, are also depicted, as is the suggestion of some form of switching arrangement permitting control over the number of flashes for a given curing requirement. Likewise, no provision is suggested for increasing the luminous intensity or for controlling the uniformity of the intensity of successive flashes.
Also, U.S. Pat. No. 4,009,382 (Nath) depicts apparatus intended for similar applications, but in which radiation is coupled to the patient's mouth by means of a UV transmissive, liquid filled channel.